Control for air conditioning systems



Patented Nov. 2l, 1950 2,531,037 CONTROL FOSR AI-R CONDITIONING YSTE William J. Hajek, Knoxville, Tenn., assignor to Robertshaw-Fulton Controls Company, Knoxville, Tenn., a corporation of Delaware Application January 2, 1948, Serial No. 276

3 Claims. l

This invention relates to a control for air conditioning systems and more particularly to such a control which prevents air heating by such asystem during the period air is being cooled by such system. v

Air conditioning systems are well known in which air to be conditioned is drawn into the system for conditioning and then discharged therefrom into the enclosure after the air has been heated or cooled as the temperature within the enclosure may require. Such conditioning systems usually include a heating coil for heating the air, which heating coil may be heated .by steam, and an air cooling coil, which may be cooled by a heat transfer medium cooled by a refrigerating unit. Temperature responsive devices are usually positioned in the stream of the air to be conditioned to either actuate the refrigerating unit to cool the air or to admit steam to the heating coil to heat the air. In known devices it is quite possible at temperatures of the air to be conditioned between that requiring cooling and that requiring heating to have the refrigerating unit in operation to cool the air and at the same time to have steam admitted to the heating coil to heat the air. This results in an undesirable and ineicient heating and cooling of the inlet air at the same time.

It is accordingly an object of the present invention to provide a control for air conditioning systems which prohibits admission of the heating medium to the heatng coil or coils of the system while the refrigerating unit of the system is in operation.

Another object of the present invention is to provide such a controlwhich may be readily installed in existing systems as well as new systems at a minimum cost; which is simple; and which is of positive and denite action.

Other and further objects of the present invention will appear from the following descri-ption thereof.

The control of my invention is capable of many mechanical embodiments one of which is shown in the accompanying drawing for purposes of illustrating this invention. This illustrative embodiment of my invention, however, is not to be construed as a deiinition or limitation of the scope thereof, as reference should be had to the appended claims for this purpose.

The accompanying drawing illustrates schematically an air conditioning system embodying the present invention.

In the drawing an air conditioning unit is generally indicated at III and includes an air inlet II for the air to be conditioned and an air discharge I2 for the conditioned air. Suitable circulating fans I3' may be provided for drawing air through inlet Il and for discharging the air through discharge I2. A suitable cooling coil I3 is mounted in the path of the inlet air and a suitable heating coil I4 is also disposed in the path of the inlet air.

Heating coil I4 is heated by steam from any appropriate source including pipe I5 that is connected to a control valve generally indicated at I6 and which will be described in more detail hereinafter. Steam passing through valve I6 enters pipe I1 which is connected to coil i4, and steam passing through coil I4 is discharged -through pipe I8.

Cooling medium is supplied to cooling coil I3 by any suitable refrigerating unit including a suitable compressor I9, driven by electric motor through belt 2l and a suitable condenser-receiver 22 as well understood by the art. The piping for the refrigerating unit may be conventional and is not shown in order to simplify the disclosure of the present invention. Cooling coil I3 is connected to the refrigerating unit in known manner and these connections are also not shown to simplify the present disclosure. Electric current is supplied to motor 20 from any suitable source by wires 23 and 24 which connect to a suitable relay 25. Relay 25 is connected to motor 20 by wires 26 and 21, and by wires 2B and 29. Relay 25 is operated by any suitable pressure actuated switch which is connected to relay 25 by wires 3l and 32, and switch 30 is actuated by a suitable thermostat including a bulb 33 subjected to the temperature of the incoming air, charged with a suitable thermosensitive medium, and connected to the pressure chamber of the pressure actuated switch by tubing 34 as well understood in the art.

Valve I6. which controls the supply of steam to heating coil I4, may be any suitable temperature responsive valve and is here shown as a hot chamber valve in which a corrugated expansible and contractible vessel 35, subjected to the temperature of the incoming steam, carries valve element 36 for cooperation with a suitable valve seat 31 so that expansion and contraction of vessel closes and opens the valve. A cylindrical stop 38 may be provided Within vessel 35 to limit its valve opening movement and a spring 39 may be mounted within stop 38 to prevent chattering of the valve. Vessel 35 and stop 38 may be carried by a suitable valve head 40 shown as secured to the valve body by a cap nut 4I with an interposed washer 4 2.

Valve head 40'is apertured to receive a tube 43 which forms a fluid tight Joint therewith and opens into the interior oi vessel 35,.tube 43 being connected to a suitable bulb 44 subjected to the temperature of the incoming air. Valve head 40 is also apertured to receive a tube 45 which forms a iluid tight joint therewith and opens into the interior of vessel 35, tube 45 being connected to a suitable manually adjustable temperature regulating device 46 provided with manual adjusting means 41.

Valve head 40 has formed thereon or suitably attached thereto a pedestal 48 upon which is mounted a suitable bulb and heater housing 49. A bulb 50 is mounted in housing 49 and is in communication with the interior of vessel through tube 5| which passes through pedestal 48 and head and forms a fluid tight joint therewith. Bulb 50 is heated by a suitable electric resistance heater 52 having electrical leads 53 and 54 that connect with wires 26 and 21 respectively. The interiors of vessel 35, tubes 43, and 5|, bulbs 44 and 50 and temperature regulating device 48 are charged with a suitable thermosensltive iiuid, preferably a vaporizable liquid.

With the embodiment of my invention set up as described, assume that temperature adjusting device 46 has been manually adjusted for a desired room temperature, thus varying the volume of fluid available in vessel 35 as is well known to the art, and that fans I3' are in operation drawing air through inlet II and over coils I3 and I4 and discharging the air through outlet I2. If the temperature of the incoming air drops below that preset at regulator 46 the thermosensitive iiuid in bulb 44 will be condensed and will draw iiuid from vessel 35, reducing the iluid pressure in vessel 35 and allowing vessel 35 to open by its own resilience or by spring action as is well known in this type of valve. Steam will then be admitted to coil I4 to heat the incoming air until the temperature of the incoming air reaches the preset temperature. At this time the uid pressure in bulb 44 will be transmitted to vessel 35 to increase the pressure therein and expand vessel 35 to close valve I6.

Should the temperature of the incoming air continue to increase the thermosensitive fluid in bulb 33 will actuate switch 30 to close the energizing circuit of relay 25 and thereby connect wires 23 and 24 to wires 26 and 21 to energize motor 20 and drive compressor I9. Cooling medium is then supplied to coil I3 to cool the incoming air.

When current is so supplied to wires 26 and 21 current is also supplied simultaneously to heater 52 which rapidly heats bulb 50. The thermosensitive uid in bulb is rapidly vaporized and passes into the interior of vessel 35 to expand vessel 35 to valve-closed position if the valve is not already closed. If valve I6 is already closed the pressure added by the vapor from bulb 50 insures the complete and continued closure of valve I6. A positivecontrol is thus ailorded which prohibits air heating by the air conditioning system during air cooling by the system.

When the temperature of the incoming air has dropped to the desired temperature the thermosensitive uid in bulb 33 will condense and switch 30 will be actuated to deenergize relay 25 and open the circuit to motor 20 and heater 52. Bulb 50 will now cool and draw fluid from vessel 35. Vessel 35 is now in condition to respond to bulb 44 if the temperature of the incoming air continues to drop.

It will now be apparent that by the present invention I have provided a novel control for air conditioning systems which prohibits heating of the incoming air during cooling oi' the air and which is simple and inexpensive and readily installed in existing systems as well as new systems.

Changes to or modications o! the above described illustrative embodiment of my invention will now be suggested to those skilled in the art without departing from my inventive concept. Reference should therefore be had to the appended claims to determine the scope of my invention.

What is claimed is:

1. In a control for an air conditioning system having air heating and air cooling coils, a valve controlling the flow oi the heating medium to the heating coil, a refrigerating unit for supplying a cooling medium to the cooling coil, an electric motor for driving the refrigerating unit, and an electric circuit for the motor, a thermostat operatively connected to said valve and subjected to the temperature of the air flowing over said coils for opening and closing said valve, and means associated with said thermostat and actuated by the closure of the motor circuit for operating said thermostat to maintain said valve in closed position as long as said motor circuit is closed.

2. In a control for an air conditioning system having air heating and air cooling coils, a valve controlling the flow of the heating medium to the heating coil, a refrigerating unit for supplying a cooling medium to the cooling coil, an electric motor for driving the refrigerating unit,

f and an electric circuit for the motor, a thermostat operatively connected to said valve and including a bulb subjected to the temperature of the air iiowing over said coils, said thermostat being charged with a vaporizable liquid and operable by changes in iluid pressure therein to open and close said valve, and means energized whenever said motor circuit is closed for supplying iluid pressure to said thermostat to maintain said valve in closed position.

3. In a control for an air conditioning system having air heating and air cooling coils, a valve controlling the ow of the heating medium to the heating coil, a refrigerating unit for supplying a cooling medium to the cooling coil, an electric motor for driving the refrigerating unit, and an electric circuit for the motor, a thermostat operatively connected to said valve and including a bulb subjected to the temperature of the air owing over said coils, said thermostat being charged with a vaporizableliquid and operable by changes in fluid pressure therein to open and close said valve, a second bulb in communication with said thermostat, and an electric heater associated with said second bulb and connected to said motor circuit for developing vapor pressure in said last named bulb and thermostat to maintain said valve closed as long as said motor circuit is closed.

WILLIAM J. HAJEK.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 2,044,427 Giesler et al June 16, 1936 2,134,498 Bailey Oct. 25, 1938 2,237,248 Denison Apr. 1, 1941 

